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Summary

Arthur Symons’s ‘The Decadent Movement in Literature’ (1893) introduced decadence to English readers by insisting that decadence should be seen as ‘[t]he latest movement in European literature’, rejecting the proposition that decadence might have any exclusively national affiliation. Authors associated with decadence are ‘transnational’ in the sense that they responded to the challenges of working in a space that simultaneously ranged across nations and reached beyond the nation as an ideologically constructed marker of identity. This transnational re-orientation affected the decadents’ taste, modes of production, and individual identities. In short, decadents were aware of inhabiting a transnational field, and they knew that this very awareness formed a key constitutive element of their notoriously slippery shared identity. Indeed, the act of questioning national identity and national feeling was an important part of the decadents’ ethos of transgression. The transnational impulse was thus intimately related to decadent modes of dissent from the bourgeois habitus and sexual morality, as well as from traditionalist requirements of conventional literature.

The Abrolhos bank, in southern Bahia State (BA), is the largest coral reef system in the southwestern Atlantic. It is highly influenced by the Brazil Current (BC), since it is located in the continental shelf. By contrast, Todos os Santos Bay (TSB), in Salvador, capital of Bahia State (BA) has an important coral biodiversity, located in a bay inlet with restricted water circulation. Coral cores were collected in those sites and were analyzed for density band counting and by Th/U dating to estimate growth rates and age. In this work, we present 14C ages of some of these bands in order to evaluate the marine reservoir effect (MRE) to which the colonies were subjected during growth. It is the first study making use of coral skeleton samples for MRE determination for the Brazilian coast. ΔR was calculated to be –151±23 14C yr, while that for the TSB was –107±51 14C yr.

The use of concrete-recycled aggregates to produce high-performance concrete is limited by insufficient correlation between resulting microstructure and its influence on mechanical performance reproducibility. This work addresses this issue in a sequential approach: concrete microstructure was systematically analyzed and characterized by scanning electron microscopy and results were correlated with concrete compressive strength and water absorption ability. The influence of replacing natural aggregates (NA) with recycled concrete aggregates (RCA), with different source concrete strength levels, of silica fume (SF) addition and of mixing procedure was tested. The results show that the developed microstructure depends on the concrete composition and is conditioned by the distinct nature of NA, recycled aggregates from high-strength source concrete, and recycled aggregates from low-strength source concrete. SF was only effective at concrete densification when a two-stage mixing approach was used. The highest achieved strength in concrete with 100% incorporation of RCA was 97.3 MPa, comparable to that of conventional high-strength concrete with NA. This shows that incorporation of significant amounts of RCA replacing NA in concrete is not only a realistic approach to current environmental goals, but also a viable route for the production of high-performance concrete.

There are few reports of cryopreservation and injuries in Macrobrachium amazonicum embryos. Thus, the aim of this study was to analyze the effects of cryoprotectants agents and cooling on stage VIII of this species. Fertilized eggs from ovigerous females were removed from the incubation chamber, then placed in 10 ml Falcon tubes with a cryoprotectant solution and saline-free calcium solution. Thus, the embryos underwent a cooling curve of 1°C per min until reaching 5°C, and then were stored for 2 h. The tubes containing the embryos were washed to remove the cryoprotectant, acclimated for 5 min and then transferred to 50 ml incubators. At the end of the 24-h period, living embryos from each tube were counted and tabulated. A pool of embryos was fixed with 4% formaldehyde and then subjected to histology using 3-mm thick sections and stained with haematoxylin/eosin. Another pool was used for biometric analysis in which length, width and volume were analyzed. The cryoprotectants agents used were: dimethylsulfoxide (DMSO), methyl alcohol, ethylene glycol at 1, 5 and 10% and sucrose (0.5 M). Variance analysis was performed followed by Tukey's honest significant difference (HSD) test at 5% significance level. DMSO cryoprotectant affected embryo survival the least with rates of 71.8, 36.2 and 0% for concentrations of 1, 5 and 10%, respectively. Ethylene glycol caused 100% mortality at all the concentrations used. It was not possible to observe the interference of cooling and cryoprotectants on embryonic structures in this study.

Summary

In this chapter, we consider the influence of the surfaces or membranes on diffusive processes. The main aim is to investigate how the surface may modify the diffusive process of a system governed by a fractional diffusion equation.

In the first part of the chapter, we analyse the one-dimensional problem characterised by time-dependent boundary conditions, showing how they influence the diffusive process in the system for an arbitrary initial condition, i.e., the quantities related to the diffusion process, such as the first passage time, which may have an anomalous behaviour. A similar analysis is carried out for the two-dimensional case with inhomogeneous and time-dependent boundary conditions. These results show the potential of this formalism to analyse other physical scenarios, such as describing the molecular orientation and the anchoring problem in liquid crystals confined to a cylindrical region, taking into account the adsorption phenomena at the interfaces.

The second part of the chapter is dedicated to investigating situations in which the processes occurring on the surface are coupled to the bulk dynamics by means of the boundary conditions. As a first application, we consider a surface in which, besides the adsorption–desorption process, a reaction process may occur and the system presents anomalous diffusion behaviour. Another application refers to the transport through a membrane of definite thickness, for which the processes occurring on the surface also couple with the diffusion equations governing the bulk dynamics. In all cases, the system may exhibit an anomalous diffusive behaviour for which surface effects play a remarkable role.

1D and 2D Cases: Different Diffusive Regimes

Surface effects are present in a variety of real scenarios of interest in engineering [112, 136], biological systems [137], and physics [138, 139] as a fundamental feature of several processes. For example, industrial and biochemical reactions can have the reaction rate or the sorption of reagents limited by the mass transfer between the fluid phase and the catalyst surface. In biological systems [140], the surfaces (or membranes) are responsible for the selectivity of particles by means of sorption and desorption processes, and, consequently, the particles transfer from one region to the other. Other contexts can also be found in physics such as the electrical response of water [141] or liquid crystals [142] in which the effects of the interface between electrode and fluid play an important role.

Summary

This chapter describes some analytical results obtained by means of a pioneering application of fractional diffusion equations to the electrochemical impedance technique employed to investigate properties of condensed matter samples. The first part of the chapter focuses on some basic aspects of the impedance spectroscopy and the continuum Poisson–Nernst–Planck (PNP) model governing the behaviour of mobile charges. In this model, the fundamental equations to be solved are the continuity equations for the positive and negative charge carriers coupled with Poisson's equation for the electric potential across the sample. The diffusion equation is then rewritten in terms of fractional time derivatives and the predictions of this new model are analysed, emphasising the low frequency behaviour of the impedance by means of analytical solutions. The model is reformulated with the introduction of the fractional equations of distributed order for the bulk system. As a step further, the proposition of a new model – the so-called PNPA model, where “A” stands for anomalous – is built by extending the use of fractional derivatives to the boundary conditions, stated in terms of an integro-differential expression governing the interfacial behaviour. Some experimental data are invoked just to test the robustness of the model in treating interfacial effects in the low frequency domain.

Impedance Spectroscopy: Preliminaries

The electrochemical impedance technique is used to investigate electrical properties of liquid materials [312]. The sample is submitted to an ac voltage of small amplitude to assure that its response to the external signal is linear. Thus, the impedance, Z(ω), is measured as a function of the frequency f = ω/2π of the applied voltage, V(t), with a typical amplitude V0. In the low frequency region, of particular importance is the role of the mobile ions regarding the value of the measured impedance because they contribute to the electrical current [152].

In this frequency region, the theoretical analysis of the influence of the ions on the electrical impedance is usually performed by solving the continuity equations for the positive and negative ions and the equation of Poisson for the actual electric potential across the sample. This is the so-called PNP model.

Summary

The preceding chapters dealt with the fractional diffusion equation with spatial and temporal fractional derivatives, diffusion coefficients with space and time dependencies, external forces, and surface effects in finite length situations. Remarkable consequences appear also when we consider the diffusion process in the presence of anisotropy.

To analyse the anisotropic case, we first face a problem in which suspended or dispersed particles diffuse through an anisotropic semi-infinite medium. The process is described in the framework of the usual diffusion equation, but anomalous diffusion behaviour arises in the system because the phenomenon of adsorption– desorption of particles occurs at the interface, and the conservation of the number of particles in the system has to be imposed.

The second problem is to consider a fractional diffusion equation subjected to an anisotropy, with a nonsingular spatial and temporal diffusion coefficient. We will show that the distribution governed by the equation is not separable in terms of space and time variables as in the usual diffusion, which is an unexpected behaviour since the fractional operator is linear. As a specific application, the chapter closes with the search for the solutions to the comb model with integer and fractional derivatives, and also with a drift term. This model is a simplified picture of highly disordered systems and can be connected with a rich class of diffusive processes due to geometric constraints.

The Adsorption–Desorption Process in Anisotropic Media

We consider first the diffusion problem in a semi-infinite anisotropic medium in contact with a solid substrate at which an adsorption–desorption process takes place [114, 210]. Initially, a defined number of particles is suspended or dispersed in the medium and an anisotropic diffusive process starts. The particles reaching the solid substrate can be adsorbed and desorbed in such a way that the kinetics of this process is governed by a typical balance equation characterising a chemical reaction of first kind (Langmuir approximation) as the one considered in Section 5.4. The conservation of the number of particles is then invoked and the profiles of the surface as well as of the bulk density of particles are analytically obtained by means of Laplace–Fourier techniques. The results for the momentum distribution show that the system exhibits anomalous diffusion [211] behaviour, according to the values of the characteristic times entering the problem.

Summary

The very irregular state of motion observed by Robert Brown for small pollen grains suspended in water initiated one of the the most fascinating fields of science. The importance of such discovery – the so-called diffusion process – is immeasurable; it has been found in many contexts and is widespread in nature. A characteristic feature of this random motion is the linear growth with time exhibited by the mean square displacement, which is typical of a Markovian process. In contrast with this situation, a large class of systems and processes present a diffusion behaviour characterised by a nonlinear time dependence of the same quantity, thus constituting what is called anomalous diffusion behaviour.

The last decades have witnessed an increased interest in the anomalous diffusion processes that seem to be indeed present in a variety of experimental scenarios in physics, chemistry, biology, and several other branches of engineering; it is a rapidly growing field of research, attracting the attention of the scientific community. This happens from the theoretical side – due to the new mathematical problems evoked – but also from the point of view of experimental or practical applications. It is noteworthy that the number of studies reporting experimental problems dealing with anomalous diffusion has strongly increased – this attests to the ubiquity of a phenomenon initially considered a rare event.

The power of the mathematical tools based on fractional calculus, on the other hand, has also attracted the attention of the community working with pure and applied mathematics. The association of these techniques with the diffusional problem represents in practice a new field of research. It was shown in several ways that fractional calculus, if it is not unique, is nevertheless a suitable or even the natural mathematical framework to use to face the high complexity represented by anomalous diffusion phenomena. One powerful way of using these mathematical tools to analyse diffusion processes leads naturally to the necessity to search for solutions of fractional linear and nonlinear diffusion equations.